NON-PRECIPITATION WEATHER TERMS

The following advisory terms are used to ALERT the public of weather situations that are not necessarily associated with precipitation, but need to be highlighted. The warning terms are used to WARN the public of non-precipitation events that could be a threat to life and/or property.

AIR STAGNATION ADVISORY

Issued when major buildups of air pollution, smoke, dust, or industrial gases are expected near the ground for a period of time. This usually results from a stagnant high pressure system with weak winds being unable to bring in fresh air.

FOG ADVISORY

Used when dense fog covers a widespread area and reduces visibilities to 1/4 mile or less, and frequently near zero. May also be called a DENSE FOG ADVISORY. In some parts of the country a DENSE FOG WARNING is issued instead of an advisory for visibilities eqaul to or less than 1/4 mile.

FROST ADVISORY

Issued in growing season to indicate formation of widespread frost. Overnight lows in the 30s will usually result in widespread frost, especially in the lower to middle 30s with light winds.

EXCESSIVE HEAT ADVISORY

Issued when daytime heat indices of 100 degrees Fahrenheit or above and/or maximum temperatures of 95 F are expected. This advisory would be issued when the heat becomes an inconvenience, and only a problem for a minor portion of the population. The threshold varies depending on the geographic region.

OZONE ACTION DAY

A "heads-up" message issued by the Wisconsin Department of Natural Resources (DNR) through the NWS when ozone levels may reach dangerous levels the next day. This message encourages residents to prevent air pollution by postponing the use of lawn mowing, motor vehicles, boats, as well as filling their vehicle gas tanks.

OZONE ADVISORY

Issued by the Wisconsin Department of Natural Resources (DNR) through the NWS when ozone levels (parts per million) reach 100. Ozone levels above 100 are unhealthy for people with heat and/or respiratory ailments.

WIND ADVISORY (also LAKE WIND ADVSRY)

Issued when sustained winds of 30 mph or greater are expected to last for 1 hour or more, or for gusts of 45 to 57 mph for any duration. Lake Wind Advisories are issued for area lakes in some of the Northern Plains states when sustained winds of 30 mph or more are expected.

WIND CHILL ADVISORY

Issued for wind chills of 20 below zero (F.) or colder for a sustained period of time. Winds are expected to be at least 10 mph. Threshold values will be "warmer" in more southern latitudes.

EXCESSIVE HEAT WARNING

Issued when the heat index equals or exceeds 105 degrees F or greater and minimum heat index of 75 F or greater for 2 days. In these cases the heat becomes dangerous for a large portion of the population. The threshold varies depending on geographical location.

HIGH WIND WARNING

Sustained winds of 40 mph or greater are expected to last for 1 hour or longer. Also issued if winds of 58 mph or more are anticipated for any duration. Some mountain locations have threshold values of 50 mph sustained for 1 hour or more, and any duration gust to 70 mph or more.

FREEZE WARNING

Used during the growing season when temperatures at/near the ground are expected to drop well below freezing (32 Degrees F.) over a widespread area for a significant amount of time, regardless of whether frost forms or not.

WIND CHILL WARNING

Issued when wind chill values are expected to reach 35 below zero or lower (upper Midwest, Northern Plains, some mountain areas) along with wind speeds above 10 mph. Other locations in the eastern or southern parts of the U.S. have a warning threshold of 25 below zero, or perhaps even "warmer."